Nitro derivatives of benzoyl leuco methylene blue



United States Patent O NITRO DERIVATIVES or BENZOYL LEUCO METHYLENE BLUE Clyde S. Adams, Yellow Springs, Marjorie J. Cormack,

Dayton, and Mary Lou Frazier, Springfield, Ohio, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Application June 27, 1955, Serial No. 518,333

3 Claims. (Cl. 260-243) This inventionrelates to the light-stable leucomethylene blue derivative 10 (nitrobenzoyl) -"3,7 bis(dimethylamino)phenothiazine, having the structure S (ormmgsgmcmn 10 N and in which R is taken from the group consisting of 4-nitro and 3-nitro.

The known unnitrated leuco compound IO-benzoyl- 3,7-bis(dimethylamino)phenothiazine, also known as benzoyl leucomethylene blue, normally is substantially colorless and has been used as a color reactant which turns to a blue-green color on prolonged contact with acid clay-like materials such as attapulgite and halloysite. It is used in conjunction with other, faster-reacting, colorless color reactants, which also are turned to the colored form on contact with such acid clay-like materials.

The present primary use of these color-reactant materials is their incorporation in transfer coatings on the rear surfaces of manifold sheets. These manifold sheets are placed over paper sensitized with attapulgite or halloysite, and an impression, by printing or writing, is made, transferring the color reactants to the sensitized surface of the under sheets, thus making an impression in color thereon. A typical manifold sheet, of the type described, is disclosed in United States Patent No. 2,646,367, which issued on the application of Chester Davis and Ned A. Thacker on July 21, 1953. In that patent, there is disclosed a base web of paper having a coating made of wax and an oil, the oil having dissolved therein the fastreacting colorless color reactant crystal violet lactone, more specifically described as 3,3-bis(p-dimethylaminophenyl)-6-dimethylamino-phthalide, which turns to a dark blue color upon coming into contact with attapulgite r halloysite, and the slower-reacting compound benzoyl leucomethylene blue, before mentioned. The crystal violet lactone color fades on prolonged exposure to light, and, as it gradually fades away, the slower-reacting benzoyl leucomethylene blue develops color, so that the printing or writing is not lost.

One drawback to the use of benzoyl leucomethylene blue is that it gradually decomposes to the colored form on exposure to light. Thus, a manifold sheet with the coated side exposed to light gradually assumes an undesirable blue-green color.

Therefore, it is the object of this invention to provide 2,783,228 Patented Feb. 26, 19 57 double salt of leucomethylene blue, having the structure To 100 grams (0.202'mole) of the zinc chloride double salt of leucomethylene blue are added 225 grams (3.5 moles) of pyridine and 75 grams (0.404 mole) of pulverized p-nitrobenzoyl chloride. The reaction mixture is reone half hour.

fiuxed gently with stirring for two hours in a three-necked, round-bottom flask fitted. with a mechanical stirrer, a reflux condenser, and a thermometer. The reaction mixture then is poured into one liter of water and stirred for The dark blue-green precipitate which forms is filtered off and washed with water. This washed blue-green precipitate is transferred to a beaker and stirred for one half hour with 40'grams of sodium hydroxide dissolved in one liter of Water. The precipitate is filtered The resulting dark benzene solution then is treated with fullers earth and filtered. The resulting orange-red filtrate is concentrated to 800 milliliters and precipitated with petroleum ether.

The resulting product, 10-(4-nitrobenzoyl)-3,7-bis(dimethylamino phenothiazine, is a crystalline material of a light orange-yellow color having the structure The 10 (3 nitrobenzoyl) 3,7 bis(dimethylamino) phenothiazine, having the structure is made by the same process except that m-nitrobenzoyl chloride is used instead of p-nitrobenzoyl chloride. This derivative also is a crystalline material of a light orangeyellow color.

The light orange-yellow color of these nitro derivatives of benzoyl leucomethylene blue is unimportant in making the described manifold paper, as it is used in such small quantities and in such thin films that the coating appears as a creamy off-color white. However, in contact with attapulgite or halloysite, they become intensely blue-green in color.

3 4 What is claimed is: 3. The substantially light-stable leucomethylene blue 1. 10 nitrobenzoyl 3,7 bis(dimethylamino)phenderivative of the formula 10-(3-nitrobenzoyl)-3,7-bis thiazine, having the structure (dimethylamiuo)phenothiazine, having the structure S S (mom-, a menu; 5 (cHmN 5 mom),

g g) \o i? in :5 R is taken from the group consisting of 44mm References Cited in the file of this patent an -n1trc 2. The substantially light-stable leucomethylene blue FO I PATENTS derivative of the formula 10-(4-uitrobenzoyl)-3,7-bis 113,721 Germany Sept. 28, 1900 (dimethylamino)phenothiazine, having the stmcture 512,300 Belgium July 15, 1952 s 725,275 Great Britaiu Mar. 2, 1955 (fllmflgfigmflflm 

1. 10 -NITROBENZOYL -3,7-BIS(DIMETHYLAMINO)PHENOTHIAZINE, HAVING THE STRUCTURE 